Credits

What will you get?

You will not have to open your box (at least not unless you make a fatal mistake)!
You will have a Debian Squeeze userland and the stock Buffalo kernel of your already installed firmware.
So it is not a full replacement of Buffalos firmware, but mostly. ;-)
To have a "complete" Debian Squeeze installation one would need to replace the kernel also. But user benoqkuke hasn't managed to build his own kernel (newer than 2.6.31) yet. So stay tuned, if you want to have a more recent kernel also.

What you need beforehand

You have to be able to use the root account on the NAS.
You can use [2] CHL-v2/XHL 1.37 Mod 1 firmware to do that.

Debootstrap

You need to install debootstrap.
To be able to do this, you need to download the package.
Log on as user root on your box and and execute this: